I put some in my 98 mxz670, lets see if I can remember, I left mains stock, for safety reasons, throttle slide ,cut from stock 2.5 to3.5, Plastic UfO center hole enlarged to 5/16, Needle valve tube- drill a small #55 drill size hole right at the bottom of the mouth of the carb where the tube sticks out into the mouth of the carb. Needle jet- cut in half, mine stock were # 60 but I used 25. This was a safe set up,dialed in with EgT gauges,3/4 to full throttle Egt temps were still plently safe could have went lower on mains. Also if you go to DNEperf.com and update your needle tubes to the 98 specs, just look under free speed. Also, when you do this it will over rev because you are making more H.P. Put some more tip weight in your lever arms to bring your rpm back to stock, finally my disclaimer,Thunder Products has the jetting specs for a 670 because they helped me get to my final jetting. I enjoyed doing this mod, throttle response was great,fuel milege decreased, not much but it's better than worse. About 2 liters less per fill up.
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